# How to Calculate Quantiles by Group in R?

• Last Updated : 23 Dec, 2021

In this article, we will discuss how to calculate quantiles by the group in R programming language.

To obtain the required quartiles, quantile() function is used.

Syntax:

quantile( data, probs)

Parameters:

• data: data whose percentiles are to be calculated
• probs: percentile value

To group data, we use dplyr module. This module contains a function called group_by() in which the column to be grouped by has to be passed.

Syntax:

group_by(column_name)

To find quantiles of the grouped data we will call summarize method with quantiles() function.

Syntax:

summarize( function )

Example 1: Calculate Quantiles by group by summarizing one quartile with probability 0.5

## R

 `# import library ` `library``(dplyr)`   `# create dataframe` `df<-``data.frame``(x=``c``(2,13,5,36,12,50),` `               ``y=``c``(``'a'``,``'b'``,``'c'``,``'c'``,``'c'``,``'b'``))`   `# create groups` `# calculate quantiles by group` `df %>% ``group_by``(y) %>%` `  ``summarize``(res=``quantile``(x,probs=0.5))`

Output:

Example 2: Calculate quantiles by group by summarizing three quartiles with probability 0.25, 0.5, and 0.75.

## R

 `# import library ` `library``(dplyr)`   `# create dataframe` `df<-``data.frame``(x=``c``(2,13,5,36,12,50),` `               ``y=``c``(``'a'``,``'b'``,``'c'``,``'c'``,``'c'``,``'b'``))`   `# create groups` `# find quantiles` `df %>% ``group_by``(y) %>%` `  ``summarize``(first=``quantile``(x,probs=0.25),` `            ``second=``quantile``(x,probs=0.5),` `            ``third=``quantile``(x,probs=0.75))`

Output:

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